It is known that microelectronic photoresists are coated onto substrates such as silicon and copper to make compositions, which, when exposed to light and developed, are useful as, for example, in the manufacture of integrated circuits.
To further increase the resolution capabilities of photoresists, dry plasma development processes were created to avoid the unpredictable image swelling which resulted from solvent developing techniques. Plasma developable photoresists are disclosed in said U.S. Pat. No. 4,278,753.
Stepper cameras have been increasingly used as light sources in photoresist production to provide better resolution, alignment, and fewer defects in the plasma developed image.
The photoresists disclosed in the said U.S. Pat. No. 4,278,753 patent are highly sensitive to a light wavelength of about 366 n.m., i.e., ultraviolet light. However, the stepper cameras operate preferably at about 436 n.m., i.e., visible light, because of the high costs involved in equipping the cameras with the quartz lenses necessary to focus 366 n.m. light. Although the Lewis patent does disclose the use of sensitizers to extend the spectral response of the photoresist compositions therein, the thus sensitized compositions have a short coated part life, i.e., after coating the composition onto the desired substrate, it begins to lose its sensitivity after a very short time, requiring exposure immediately after coating. Therefore, the need exists for a photoresist that is sensitive to visible light while maintaining an acceptable coated part life.